The studies described in this research project are designed to provide information on the nature of the chemical and physical interactions leading to the formation of rhodopsin from opsin and 11-cis-retinal. At the present we are focusing on two major areas: 1) The role of lipid in the regeneration reaction and 2) The structure of rhodopsin. The role of lipid is being addressed by looking at the kinetics of regeneration of delipidated rhodopsin reconstituted with exogenous lipids. The other aspect under study is an attempt to obtain three-dimensional structural information on rhodopsin. To date we have been able to prepare microcrystals of rhodopsin that can be visualized via electron microscopy. These studies are continuing in an effort to optimize the crystal size and begin image reconstruction.